Crystalline Cellulose in Hydrated Primary Cell Walls of Three Monocotyledons and One Dicotyledon

The molecular ordering of cellulose, including its crystallinity,in the unlignified primary cell walls of three monocotyledons(Italian ryegrass, pineapple, and onion) and one dicotyledon(cabbage) was characterized by solid-state ¹³C NMR spectroscopy.These species were chosen because their primary cell walls havedifferent non-cellulosic polysaccharides and this may affectthe molecular ordering of cellulose. Values of the proton rotating-framerelaxation T_1p(H)] and spin-spin relaxation T₂(H)] time constantsshowed that the cellulose in the cell walls of all four specieswas in a crystalline rather than an amorphous state. Furthermore,a resolution enhancement procedure showed that the triclinic(I) and the monoclinic (I_rß) crystal forms of cellulosewere present in similar proportions in these cell walls. However,the calculated cross-sectional dimensions of the cellulose crystallitesvaried among the cell walls (in the range 2–3 nm): thelargest were in the Italian ryegrass, the smallest were in theonion and cabbage, and those of intermediate size were in thepineapple. The crystallite dimensions may thus be affected bythe non-cellulosic polysaccha-ride compositions of the cellwalls. ⁴Present address: Food Science Postgraduate Programme, Departmentof Chemistry, The University of Auckland, Private Bag 92019,Auckland, New Zealand.